Diamond is a wide bandgap semiconductor with an indirect gap of about 5.47 eV, thereby supporting high electric fields before breakdown. High purity chemical vapor deposition (CVD) diamond also has high mobility and long lifetimes for electrons and holes, in addition to high thermal conductivity. These properties make diamond suitable for many applications.
For example, diamond can be used to control power at high voltages due to its wide bandgap. A single diamond switch can be used to switch power at voltages approaching 50 kV, which is challenging for other electronic materials, such as Si and Ge. In another example, diamond can be used for radiation detection, especially in situations where volume sensitivity, radiation hardness, and temperature insensitivity are desired. In contrast to many other solid state radiation detectors, which use reverse biased diodes, high purity intrinsic diamond can act as a solid state ionization chamber at room temperature because charges can travel freely through the lattice of diamond with good purity and crystalline quality.
Currently, diamond membranes (also referred to as diamond films) are usually fabricated via CVD on a non-diamond substrate, such as silicon, tungsten, and titanium. However, the lattice constants of these substrate materials typically do not match the lattice constant of diamond. This lattice constant mismatch can introduce strain into the epitaxial diamond layer, thereby preventing epitaxial growth of thicker diamond layers without defects.
Alternatively, diamond films can also be deposited on a diamond substrate. In this case, one diamond substrate usually fabricates only one diamond membrane so the cost is high. Reuse of diamond substrates can be challenging because it is difficult to remove the fabricated diamond membrane without damaging the surface of the diamond substrate. For example, chemical lift-off as often used in industry can be slow, and the etching residues tend to become surface contamination after release. Another method of removing fabricated diamond layers is the optical lift-off technique, which releases the fabricated diamond membrane via selective heating. However, the heating can roughen the substrate surface and the local pressurization at the membrane-substrate interface caused by high-power thermal irradiation can induce cracks or dislocations.